Conventionally, as a bright pigment such as a pearlescent pigment, a pigment in which each of flaky particles such as mica flakes, synthetic mica flakes, silica flakes, alumina flakes, glass flakes, or graphite flakes is covered with a covering layer containing a metal oxide such as titanium dioxide or iron oxide, iron oxide particles containing α-iron oxide crystals as a main component, and the like have been known. Those pearlescent pigments glitter by reflecting incident light from the outside on surfaces thereof, and impart unique surface appearances that are varying and have beautiful effects to a coating surface when blended with a paint, to a drawn line or a printing surface when blended with ink, or to a surface of a resin molding when blended with a resin composition, together with color tones of various substrate surfaces thereof.
In order to enhance beauty, the pearlescent pigments have been used widely for various applications such as an automobile, a motorcycle, office automation (OA) equipment, a mobile phone, a household electric appliance, various printed matters, and writing instruments.
Titanium dioxide has three kinds of crystal forms including anatase, brookite, and rutile. Of those, anatase and rutile titanium dioxides have been produced industrially. Anatase titanium dioxide has a high photocatalytic activity, and hence accelerates the degradation of components and discoloration of a resin composition and a paint composition. On the other hand, rutile titanium dioxide has a photocatalytic activity that is about one tenth of that of anatase titanium dioxide and is suitable for being blended as a pigment with a resin composition or a paint composition.
JP 2002-509561 A and JP 2010-538096 A propose a pearlescent pigment in which a flaky substrate is covered with a metal oxide layer containing rutile titanium dioxide, as an example of an interference pigment.